Process of cleaning coal



April 21, 1931.

R. w. ARMS PROCESS OF CLEANING GOAL 3 Sheets-Sheet 1 Filed Aug. 24, 1928 Mai/was April 21, 1931. w, AR g 1,801,254

PROCESS OF CLEANING COAL Filed Aug; 24, 1928 3 Sheets-Sheet 2 fnyeiflor 270 0 5. Jrwas' Jzfarneys.

April.21, 1931. R. w. ARMS 1,801,254

PROCESS OF CLEANING COAL Filed Aug. 24, 1928 3 Sheets-Sheet 3 RAY W. AR

Patented Apr. 21, 1931 UNITED STATES PATENT OFFICE MS, OF CHICAGO, ILLINOIS, ASSIGNOR TO ROBERTS AND SCHAEFER COM- PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS PROCESS OF CLEANING COAL Application filed August 24, 1928. Serial No. 301,739.

My invention relates to a process of cleaning coal and refers especially to that part of the coal cleaning process which involves the handling and segregation of the dust resultant from any air treatment of coal. One ob ject of the invention is to carry on a process whereby the air which assists in coal cleaning may be reused a number of times as it passes through the system and whereby only a minimum amount of dust laden air will be finally discharged. from the system for separate positive dust separation. A suitable apparatus for carrying out this process is dis cussed below and illustrated in the drawings. In general I propose to provide a series of batteries of air cleaning tables, all the tables in each battery preferably handling coal of the same general size and having the same general air requirement but the tables in different batteries handling coal of considerably different sizes and having considerably difierent air requirements though under some circumstances the limitation as regards size and air requirements of the table 5 in any particular battery may be dispensed with, in which case we would have a series of different batteries having different air reqpirements and handling different sized coa I I propose to associate with each battery no matter what its character and no matter what the air requirement of the battery is a plenum chamber which is merely a relatively large size chamber through which aircirculates at relatively low velocity. The working air for each tablein the battery will be supplied from this plenum chamber, the pressure in the plenum chamber being provided by a single fan, pump or blower.

Preferably the plenum chamber which supplies air to the battery handling the finest coal will receive its air supply from the outside atmosphere or from the dust collector. The plenum chamber for the other batteries will receive dust laden air drawn from hoods enclosing the tables of the preceding battery and such plenum chambers will serve also as settling chambers being preferably equipped with a screw conveyor at the bottom which will. take out the large particles settled out from the dust laden air.

Each table will be provided with a hood and the air will be drawn from this hood into the next plenum chamber but since it is necessary to have openings between the hood and the table to permit workmen to inspect the operation and to permit coal to pass to and be discharged from the table, there will always be a certain amount of clearance and the suction pipe that leads from the hood to the plenum chamber will draw in the spent dust laden air which is passed up through the deck plus a certain amount of make-up air approximately perhaps twenty per cent of the total.

The air requirement of each succeeding battery is generally greater than the air requirement of the preceding battery and if the make-up air that is drawn in around the hood is suflicient, no further attention is required. If, however, it is not suiiicient, I propose to discharge into that plenum chamber dust laden air from some other source as for instance from the classifying screen or from bucket elevators, conveyor lines or any other place about the plant where dust laden air may be found. If on the other hand, the air requirement for a succeeding battery is less than for a preceding battery, I Will discharge air from the succeeding plenum chamber to the dust line leading to the dust collector.

The dust laden air from the hood enclosing the last battery in the series is conducted by the dust line to the dust separator and into this dust line will also discharge dust laden air from any of the sources of dust laden air other than the tables above referred to which may be left over after the system In general, we will then have a system :i'

from to the plenum chamber and through the passages leading from the plenum chambers to the deck. This system can and must be made dust and air tight as otherwise power will be lost. All other parts of the system are under suction and so any leakage merely results in adding to the amount of air which must be handled but does not result in the discharge of dust out of the system. This applies not merely to the tables but toscreens, conveyors and other elements of the system so that all the dust which would otherwise be present in the air in the working part of the house causing the possibility of a dangerous dust situation or making working conditions unpleasant will be avoided. I

Experience shows that by this re-use of the air the total power required to handle dust laden air after its work has been done, and the capacity of the dust collector required to take the dust out of the air is reduced to a minimum. This latter is especially important because the size and expense of the dust collector depends not upon the amount of dust present but upon the total volume of air which must be handled.

My invention is illustrated more or less diagrammatically in the accompanying drawings, wherein-- Figure l is a diagrammatic view showing one form of the exemplification of my solution of the problem; 7

Figure 2 is a section along the line 2.2 of Figure 1;

Figure 3 is a view similar to Figure 1 showing a difierent solution of the problem having, however, features of similarity. Like parts are indicated by like characters throughout the specification and drawin "s.

A is a dust collector adapted to take out substantially one hundred percent of the dust from the air. A is a passage leading therefrom to a fan or blower A driven by a motor A This fan or blower A discharges through a passage A into a plenum chamber A It will be noted that thisplenum chamber is of. relatively large cross sectional area; so large'that air as it passes through it having been forced thereinto by the blower A will always move at relatively low velocity. A, A are a series of coal separating tables or decks fed from the plenum chamber A through conduits A diecharging into vas chimneys A which in turn discharge and conduct air through the screen or deck A. A A are hoods overlying each deck extending down'thereabout but so disposed that there is a certain amount of clearance between the deck and the hood. A is a dust manifold adapted to draw dust laden air from each of the hoods A and conduct it through the pipe A and dis-v charge it into the suction side of the blowe A driven by the motor A.

The blower A discharges through a pipe B into a plenum chamber B The blower A and the plenum chamber B are of larger capacity than the blower A and the plenum chamber A because the blower and plenum chamber must handle and contain not merely the air that is handled and contained by and in the blower A and chamber A but that air-plus twenty percent or more addi tion which has entered into the system through the hoods associated with each of the tables'A". B B are cleaning tables or decks preferably adapted to handle larger coal and requiring more air than the decks A. These decks are supplied with air under pressure from the plenum chamber or conduit B through the pipes B and vas chimney B The fact that these tables re quire more air than the tables A is provided for by the fact that we have now available in the plenum chamber or conduit B more air than we had in the plenum chamber or conduit A because of the make-up which comes in vbetween each hood and its table. B B are a series of hoods associated with the tables B communicating with the exhaust manifold B which in its turn discharges to the intake side of the fan 13 whence the air is drawn into the plenum chamber B The air is drawn from the plenum chamber 13 through the blowers C discharged thereby through the passages C the vas chimney C the deck C to take care of larger sizes of coal having an even larger air requirement. This deck C is enclosed by the hood 0* and the suction manifold C leads from each of the said hoods and communicates with the dust pipe C. This dust pipe extends to and discharges into the suction side of the blower C and thence is dis charged into the dust arrester A from which part of the dust laden air is drawn. The balance escaping out from the pipe G is dust free air or at least air sufficiently dust free to be discharged into the'atmosphere by the plant.

The above discussion concerns itself only with'the air originatingin the cleaning systems. My arrangement, however, is intend.- ed to be used in connection with plants where there are other sources of dust laden air. These have been illustratedmore or less generally wherein 1) indicates an Arms classifying screen such as adapted to separate the coal into various sized classes such as are fed to the various tables. Air is drawn from the hood D associated with the screen through the conduit D and discharged throughthe conductor C, since it is under suction it draws the dust laden air in from the Arms screen to discharge it to the dustarre ster. D represents a hood over a so-calledMarcus conveyor and picking screen. Dust isdrawn from this hood through the conduit D and may be discharged thence from the conduit D to the conductor 0 whence it goes to the dust arrester or if it is necessary to have ad ditional air for make up in the second battery of screens, the dust laden air will be passed through the duct D to the intake side of the blower A. On the other hand, in connection with the plenum chamber B we might have an excess of air from the intermediate battery for what was needed for the coarse size battery of tables in which case air could lead out from the plenum chamber B to the pipe D over the valve D to discharge again into the conduit C.

Obviously it might be possible to dispense with some of the fans here shown. Under some conditions a connection between the manifold B and the plenum chamber 13 might take the form of a simple conduit though of course this would result in changing the plenum chamber from a pressure chamber as it is shown in Figure 1 to a suction chamber and this would, of course, make it impossible to bleed off air therefrom to the conduit D as is shown. The same situation might prevail in connection with the blowers A and C"; in some conditions blower A could be dispensed with.

The essential characteristic of this arrangement is that the tables are arranged in a series of groups, all the tables in a group receiving their air from a single air source and discharging their spent air from hoods above each table to a single discharge receiving member. The air so discharged may be then used to furnish air for a next series of tables or may be passed through a dust arrester as the case may be but the general arrangement is such that We have interposed between groups of tables pressure manifolds and suction manifolds so arranged thatthe general path of air is from that part of the system where the tables require a small amount of air through the system and through the table gradually increasing in air requirement back to a dust collector from which some of the air returns to the system and the remainder is discharged from it.

In a somewhat similar but modified form shown in Figure 3 the dust collector E provides pure air which passes out through the pipe E to a blower E driven by a motor E The blower provides air under pressure to the plenum chamber or manifold E The spent air is caught in the hoods E and drawn up into the dust collecting manifold E which manifold is under an inactive pressure owing to the fact that the blowers E E are drawing air out of it. These blowers discharge air into the manifolds or plenum chambers E E from which the air is discharged from the pipes E E to the decks E E From the decks E the air is caught in the hoods E and suckedinto the. dust collecting manifold E The blower F draws the air out of the manifold E discharging into the pressure manifold F whence it is forced into the decks F hoods F 3 and into the suction manifold F which communicates with the main suction pipe F, the blower F drawing dust laden air out of that pipe and discharging itinto the dust arrester E. The dust collecting manifold F is fed from the hoods F associated with the tables E Air being drawn into that manifold by the blower F is dis charged therefrom into the pipe F.

The auxiliary apparatuses in the house are taken care of by hoods G, associated in this case with two Arms screens, and the hood G in the Marcus house both of which discharge through pipes G G respectively into the suction pipe F and by the hood G discharging through a pipe G either into the suction pipe F or into the dust collecting manifold E as the case may be to provide additional make-up air atthat point.

As illustrating the actual operation of devices such as this, we refer to Figure 1. e find that each of the tables A requires five thousand cubic feet of air. Therefore the blower A must furnish twenty thousand cubic feet to the plenum chamber. There will be drawn out of each of the hoods A 6,000 feet of air so that a total of 24,000 cubic feet from the hoods A is forced by the blower A into the plenum chamber B It happens, however, that this is not enough for the next stage in the system and so We draw 2,000 feet from the hood D over the Marcus chutes giving us a total of 26.000 feet forced into the plenum chamber B The two decks B on the left require 5,000 feet each, the two decks B on the right require 8,000 feet each which makes our 26,000 feet. From the two hoods B on the left is drawn 6,000 feet, that includes the 5,000 feet forced into the deck and 1,000 feet leakage in and around the hood. From the two hoods on the right is drawn 96,000 feet each or a total of 31,200 feet forced by the blower B into the manifold B The two decks receiving air from the manifold B however, only need the one on the right 12,000 feet, the one on the left 10,000 or a total of 22,000 feet, therefore, the 9,200 feet passes out through the pipe D into the pipe C where it joins the 6,000 feet drawn from the Arms screen from the hood D, the 26,400 feet discharged from the hoods C made up 14,400 feet from the left hand hood and 12,000 feet from the right hand hood, all of which dust laden air plus 3,000 feet in addition drawn from the hood D through the pipe D is forced by the fan G" into the dust arrester. The total amount of air thus displaced being 44,600 feet. Since the air required for the manifold A is only 20,000 feet there is discharged from the dust arrester 24,600 feet.

It'will be noted in this arrangement that the biggest fan in the system,'the one that takes all the dust laden air there is and feeds it to the dust arrester only displaces 44,600 feet. If the air was not reduced as indicated, this dust separator fan would have to handle 26,000 feet from the A tables in the first battery, 31,200 feet from the-B tables in the second battery, 26,400 feet from the two C tables in the thirdbattery, 6,000 feet from the Arms screen hood D and'5,000 feet from the auxiliary Marcus and otherchutes and hoods D or a total of 94,600 feet of air. In other words, by reducing this air I more than] cut in half the amount of air'which must be circulated through the dust arrester, thereby reducing the size of the dust arrester and the power required .to operate it.

A similar analysis of the arrangement set out in Figure 3 is hardly worth making. Suffice it to say, that in this arrangement the fan F discharges into the dust arrester 61,000 cubic feet of air. Against this, the

fan would have to handle a maximum of 112,600 feet if my arrangement were not used.

.It will be noted that there is involved in each of these two systems or in any system made according to this general plan, a series of manifolds or plenum chambers where low air velocity prevails. These plenum chambers containing as they do dust laden air furnish an especially effective separating zone where the velocity carried dust may be separated out. The veryfind floating dust is not separated but relatively large particles such as, may have been drawn out by the air blast drop to the bottom and are carried out by the screw conveyors whichare located'in the bottoms of these manifolds as are indicated by letter H in Figure 3. a

I claim: 7 r I v 1. The process of cleaning coal-by air which consists in providing a flowing stream of air under pressure, dividing such an into aplurality of parallel streams, forcing each stream through a flowing bed of coal, drawing off the spent dust laden air from above each such bed and entraining with it an additional supply of air, bringing such drawn off air together into a single stream, then dividing such stream into a plurality of separate parallel streams of dust laden air and forcing each such stream through aseparate flowing bed of coal, drawing off the resultant dust laden air from above said beds of coal, entraining with it an additional supply of aid concentrating the air thus drawn off into a single stream and separating dust from the air.

2. The process of cleaning coal by air which consists in providing a flowing stream of air under pressure, dividing such air into a-plurality of parallel streams, forcing each stream through a flowing bed of coal, drawing off the spent dust laden air from above each such bed, bringing such drawn off air together into a single stream, then dividing such stream into a plurality of parallel streams of dust laden air and forcing eachsuch stream through a flowing bed of coal arranged in series in the air stream with respect to the first mentioned beds of coal, drawing off the resultant dust laden air from above said latter beds of coal, concentrating the air thus drawn off into asingle stream and separating dust from the air. V

3. The process of cleaning coal by air which consists in forming a stream of air under pressure, dividing such stream into a plurality of streams and forcing each through a flowing bed of coal, drawing ofi the spent dust laden air from aboveeach bed, and en-. trainingwith it an additional supply of air, concentrating the air thus drawn off into a single stream, adding to such air stream an additional supply of dust laden air from an exterior source, dividing the resultant stream of air into a plurality of streams, forcing each through a flowing bed ofcoal, drawing off the spent dust laden air from above each bed, entrainingtherewith an additional supply of air, concentrating the air thus drawn off into a single stream, dividing such stream into a plurality of streams, forcing one of said streams through a flowing bed of coal, drawing off from above such bed of coal the dust laden air, entraining with it additional air, mixing the resultant stream with a dust laden stream from an exterior source and separating the dust from the air in the resultant stream.

4. The process of cleaning coal by air which consists in forming a stream of air under pressure, dividing such stream into a plurality of streams and forcing each through a flowing bed of coal, drawing off the spent dust laden air from above each bed, concentrating the air thus drawn off into a single stream, adding to such air stream an additional supply of dust laden air from an exterior source, dividing the resultant stream of airinto a plurality of streams, forcing each through a flowing bed of coal, drawing oif the spent dust laden air from above each bed, concentrating the air thus drawn off into a single stream, dividing such stream into a plurality of streams, forcing one of said streams through a flowing bed of coal, drawing off from above such bed of coal the dust laden air, mixing the resultant stream with a dust laden stream from an exterior source and separating the dust from the air in the resultant stream. 7 V

5. The process of cleaning coal by air which consists in passing a stream of air under pressure through a series of groups of coal cleaning zones of varying air requirements,

the stream of air being divided into a stream for each zone in a group, drawing off from each zone the spent dust laden air and entraining with it an additional supply of air, drawing into the system where needed to provide adequate dust laden air from outside sources where there is an excess of dust laden air drawing it oif from the system and at the end of the system withdrawing the dust laden air from the zones having the largest air requirement mixing all the dust laden air drawn off to form a single stream of air and separating dust from such stream.

Signed at Chicago, county of Cook and State of Illinois, this 18th day of August,

RAY W. ARMS. 

